The present invention relates generally to rotary actuators and more specifically to rotary actuators having improved fault-tolerance.
Rotary actuators are the most common drivers of our machines. The partial or complete failure of an actuator can cause a life threatening accident, result in costly downtime, or prevent the continuation of a critical long-duration process, such as micro-surgery. In certain applications, it is crucial that the actuator continue to function even in the event of a fault or failure in the system. Such a fault might occur, for example, in the electronics, wiring, sensors, prime mover, or gear train of the system.
Continued operation under a fault is especially desirable where long-duration missions are involved, where human life is at stake, or where a large economic loss would occur. Fault-tolerant designs have been developed incorporating excess actuators into the system in order to create an excess of inputs, thereby creating a redundant system. In such systems, this redundancy then necessitates that a huge number of decisions must be made in real time at the system level in order to get the whole system to reliably produce a desired output motion or force. Owing to inherent resulting output uncertainty, this approach is still largely a laboratory approach that is rarely used in industrial production systems.